I played flip cup with my kids and they dug it. This activity doesn't last very long tho - rounds go by pretty quick.
Since I have a pretty big class (~30 kids), I split them into teams and make sure each team competes with another team one time. If one team has a more members, just have someone on the other team go twice.
ex/ team 1, 2, 3, 4:
1 vs 2, 1 vs 3, 1 vs 4
2 vs 3, 2 vs 4
3 vs 4
And then the winners are the teams who won the most rounds.
Thanks so much for this idea!!! The kids were into it.